Inconsistent bleach quantity to FC increase in PoolMath

[mgtfp]

replying to an old post but the original issue/question does not seem to be answered and I have the same issue, in the App, setting the SLAM button on sets my SLAM target FC to 14 from the actual 4.5 I have now. This suggests to add 233 oz of 2.88% bleach by volume to reach target (increase of 9.5). If I go to the effects of adding section and put the amount to the suggested values of 233oz, FC rise would be of 18.0, in this section I would only need to add 124 oz to get a 9.5 rise in FC. which section of pool math is correct.

The 233oz look right to me.

PoolMath internally assumes that a "Bleach-Percentage" above 10% must be from "pool liquid chlorine" where the percentage shown on the bottle usually is "Trade-%", whereas values below 10% must be from "household bleach" where the percentage shown on the bottle usually is "NaOCl weight-%".

In the main section of PoolMath, this internal automatic conversion seems to work as intended, whereas in the "Effects od Adding" section something goes wrong. The shown 124oz correlate with about 5.3% bleach strength (as NOCl weight-%) that PoolMath assumed for the calculation instead of 2.88%.

Playing around with the numbers in "Effects of Adding", it looks like percentage values below 5.25 are internally always treated as 5.25%, resulting in an FC change of 9.5 for 124oz added to 5500gal.

And in the case of the OP (@jesper), bleach-percentages in "Effects of Adding" seem to be cut off at 12.5% at the upper end.

@Leebo, does my interpretation make sense?

Looks like "Effects of Adding" only works with bleach-strengths between about 5.3% and 12.5%, which seems to be the typical range in the US. That seemed to be a problem for the OP from Cyprus with 15%-bleach, and now for @Planenuts with 2.88%-bleach. It also is a problem in Australia, where household bleach usually comes as 4.2 NaOCl weight-%. And some useres probably get confused when estimating the effect of adding old bleach that has lost its strength.

 

[Planenuts]

thank-you MGTFP, it confirms my thoughts, up to now I would always use the estimate the effects to get the quantity of chemicals to add to the pool (MA, calcium chloride, stabilizer) now I know to use the 'log page'

 

[mgtfp]

Yep, the 'log page' is always more accurate, e.g. regarding influence of TA on required MA amounts to adjust pH. On the other hand, 'effects of adding' sometimes gives information on 'side effects' that you don't get from the 'log page', like effect on TA when adding MA, or effect on pH when adding CYA.

It would be nice to get these 'side effects' from the 'effects of adding' also with the recommendations on the 'log page', and if the effects on both pages were consistent, e.g. consideration of TA for acid additions, and consistent effects by bleach additions.